Problem: $ { \left[\begin{array}{rrr}{2} & {-2} & {3} \\ {1} & {2} & {-1}\end{array}\right]+\left[\begin{array}{rrr}{-1} & {-1} & {-2} \\ {1} & {2} & {4}\end{array}\right] = {?} } $
Solution: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{2}+{-1} & {-2}+{-1} & {3}+{-2} \\ {1}+{1} & {2}+{2} & {-1}+{4}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {-3} & {1} \\ {2} & {4} & {3}\end{array}\right]}$